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E. Odlund, F. Harms, J. Charton, L. Sawides; A Novel Stroboscopic Technique for Assessing a Deformable Mirror’s Ability to Perform in Ophthalmic Applications. Invest. Ophthalmol. Vis. Sci. 2008;49(13):4198. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To develop and test a method for complete temporal and spatial characterization of deformable mirrors (DM). In particular the method is suitable to characterize DMs used in adaptive optics (AO) systems for ophthalmic applications and thereby objectively evaluate their ability to correct for ocular aberrations.
An AO test bench was developed to study a DM using a stroboscopic controlled laser diode as a light source and a Shack-Hartmann wavefront sensor (WFS) as measuring device.The stroboscopic technique was employed in order to measure wavefronts at frequencies significantly higher than the repetition rate of the WFS. The devices used in the current setup were a HASO 32 OEM with 1024 microlenses and a repetition rate of 30Hz, and a laser diode that was capable of emitting light pulses with lengths as short as 100µs. We synchronized the mirror actuator signals and the stroboscope signal, then introduced and adjusted a phase delay between them.This characterization method was tested using a mirao52-d (Imagine Eyes, France) electromagnetic DM with 52 actuators. First, we defined various voltage arrays generating surfaces that mimicked the wavefront aberrations of typical eyes, including those found in highly-aberrated eyes, up to 50µm peak-to-valley (PV). Next, these voltages were applied to the mirror with a sinusoidal modulation at varying frequencies and the mirror’s temporal response was studied.
The stroboscopic probe at a frequency of 10kHz provided a 300-fold increase in sampling rate when compared to the WFS alone. This allowed us to analyze in detail the temporal response signals’ properties at frequencies up to 1.2kHz.Using this method, we observed a bandwidth of approximately 200Hz for the electromagnetic DM. The system allowed us to test wavefront errors of amplitudes ranging between 0-50µm PV.
The proposed method enabled temporal characterization of a DM using a WFS capable of measuring large aberrations with high accuracy, without being limited by the sensor’s relatively low temporal resolution. The method presents a low-cost technique for assessing DM performance for use in AO systems with ophthalmic applications.
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